stocking (p. 10) to normal stocking." 
results of previous investigations (72, 75), under- 
According to 
stocked stands tend to approach normality, at a 
relatively slow rate where understocking is due 
principally to holes or gaps in the stand, and at a 
relatively rapid rate where it is due principally to 
wide spacing of the trees. Understocking in the 
forests as mapped in the survey is due primarily 
to the presence of gaps in the stands too small to be 
mapped on the scale adopted, and only secondarily 
to wide spacing of trees. The fact that no allow- 
ance was made for improvement of stocking with 
time contributes another element of conservatism 
to the growth estimates. 
The growth rates used for the hardwood types 
were derived from an empiric yield table based on 
field sampling done as a part of the forest survey 
of Lewis County, Wash. 
The growth rates used are rates of net growth; 
that is, they represent stand increment due to 
growth of merchantable-sized trees and to the pass- 
ing of small trees into the merchantable-size class 
minus volume lost through normal tree mortality. 
Because the yield tables from which the rates were 
derived show only volume in living trees at 10-year 
age intervals, they do not include the growth in 
trees that under present practices are lost through 
suppression but that could be utilized through 
intermediate cuttings and thinnings. Hence, in- 
tensive forest management would result in realiza- 
tion of growth greater than is indicated by the 
survey calculations. 
Kinds of Growth Calculation Made 
In this project four kinds of volume growth 
calculation were made: (1) Current annual growth, 
the annual increment of stands in their present 
condition; (2) realizable mean annual growth, an 
approximation of the growth that will actually 
occur in the future under forest practice as main- 
tained in the past; (3) potential annual growth, 
11 A normal stand, or fully stocked stand, is one that, so 
far as any practical consideration is involved, utilizes its site 
completely, that is, represents the full productive capacity 
of the land on which it is growing. Normality of stand is 
determined not only by number of trees per acre but also by 
spacing of trees. The condition referred to as normal stock- 
ing is not maximum stocking. 
5D 
Ficure 16.—Second-growth western hemlock and Sitka spruce 
stand approximately SO years of age. This type is found only 
within a few miles of tidewater 
the average annual growth that could be obtained 
on the whole of the region’s commercial forest land 
through intensive forest practice; and (4) periodic 
growth, the estimated growth within a given 
interval—in this study, 10 years. he predomi- 
nance of conifers in the forests of the region has been 
previously pointed out. Although 10 percent of 
the growing stands are hardwood, less than 2 per- 
cent of the total area of forest land is true hardwood 
site and only a little more than 1 percent oak- 
madrone woodland site. In addition, much of the 
hardwood site is considered potential agricultural 
